Skip to 0 minutes and 1 secondHello and welcome to the question and answer session on week three of the practical chemistry course. My name is Mark, and I'm hopefully gonna answer few of the questions that people have posted this week. Andrew asks a question, how can we help students who are so motivated with the practical work engage but with the theoretical side of chemistry. Part of that comes down to how we mix up the practical work with theoretical aspects. And if they're interspersed together, it can help students if they have to go through a theoretical block before they get to the next aspect of practical work.

Skip to 0 minutes and 34 secondsAlso, if we consider how we put the context of the practical work and the theory into things that students can relate to and find interesting. Some of the theoretical aspects can be quite dry. So part of our role is to try and make them engaging for our students and mean something to them. For example, rates of reaction is not a particularly engaging topic for many students. But the context for rates of reaction, such as the rate limiting step in a reaction, can be determined by looking at when they come to school or college in the morning. What is it actually that limits them getting to school?

Skip to 1 minute and 5 secondsIs it that they get out of bed on time, is it they have their breakfast, is it the bus they have to wait for? And that's the thing that actually limits how fast that reaction can go. And we can then apply that in the context of the chemistry. Christine's asked a question which is about striking the balance between recipe following and allowing students the option to explore for themselves how to do the practical work. It's a difficult balance to achieve. But this can often be done if you consider how students approach the practical. Do they learn the techniques first? In which case a recipe might be appropriate.

Skip to 1 minute and 38 secondsAnd then move to applying their knowledge in a different circumstance where that's possible. So for instance, learning step by step how to do a titration. And then using those skills where they're given a more unknown solutions to look at, and given a variety of equipment, and they choose those themselves. Sometimes giving students only part of a recipe with gaps missing so they have to fill in the gaps. Or they have to do, for instance, a card sort where they're having to put the practical stages in an order themselves before they do it, can help them actually develop the practical work.

Skip to 2 minutes and 10 secondsSteven's asked a very good question about our thoughts on giving students data to analyse in a lesson, rather than the students capturing the data themselves. And this can be an absolutely perfect way to deal with the pressures of time in a curriculum. And also give students access to a large amount of data which they can analyse, rather than maybe the limited set that they or their classmates would achieve. So if the learning outcomes are aimed solely at analysing data, then you might not want to do the practical.

Skip to 2 minutes and 37 secondsOr you might combine it where students have a go to get one set of data, but then use a larger data set provided by the teacher for them to do their analysis on. Thomas has asked two very good questions. The first one is, under what circumstances should you abandon a practical if it's not going well? The first key one is if something goes wrong with equipment, or it's obvious that, for some reason, the reagents aren't working, it's best to stop the practical. Move it to another day, if that's appropriate, and carry on with other parts of it, maybe covering some of it in theoretical detail.

Skip to 3 minutes and 7 secondsAlso, if students are starting to struggle with the technique and it's clear they're not gonna get any results, it may be a good time to stop and actually maybe practice some of those techniques that students are finding difficult. That does come down to knowing your students well and also deciding what is it you actually want from the practical, and being very, very clear with your learning outcomes. Because it may be the skill of doing something that you want to try out. It may be problem finding that you want to try with students, as well, on some practicals. Why doesn't something work? As an example, we often talk about acid rain reacting with limestone and calcium carbonate based rocks.

Skip to 3 minutes and 43 secondsAnd if you try to mimic acid rain, which is with sulfuric acid, you find that if you pour that on marble chips it starts reacting and then suddenly stops. Whereas, if you use hydrochloric acid, the reaction keeps going, and we mentioned that earlier on in the course. And because we get this layer of insoluble sulfate form on top of the calcium carbonate. And students could be prompted to investigate why some acids react, and some don't, leading them to those conclusions. Even though, at first glance, that practical doesn't seem to work properly.

Skip to 4 minutes and 13 secondsThe second question that's being asked is if you've got students who have got behavioural difficulties or if the class is challenging in some way, how can you get students to safely carry out those practical activities? And quite often that can mean chunking activities into much smaller ones. As we've mentioned previously in the course, if the skills are not about the weighing or the measuring, then having preweighed or premeasured out solutions and solids, or even pre-setup glassware, can help focus students on just the bit they need to do. Also, making sure that everyone is engaged.

Skip to 4 minutes and 45 secondsSo if you are having to work in larger groups, then making sure that everyone in that group has clear tasks that they have to do, so they don't find the opportunity to get distracted or start to develop behaviour issues. One of the things we'd strongly recommend is that you don't use the withdrawal of practical science as a punishment for students, because the class can't behave or an individual can't behave. But find ways around that by making smaller practicals using less quantities, using safe equipment, or more everyday objects instead of more classic expensive equipment. Anthony asked questions about support with developing learning outcomes and success criteria.

Skip to 5 minutes and 23 secondsAnd I would strongly recommend, if you haven't done this already, to have a look at the biology course which is running in conjunction with this course. Because that has a great set of activities based on determining learning outcomes and success criteria. It's very important when looking at the practical side of things to think about what it is, that single or couple of things that I really want to get out of this practical. And then thinking, how will students be able to demonstrate to me that they can actually do that well? And sharing that clearly with the class.

Skip to 5 minutes and 51 secondsAnd trying that out for just one learning outcome per practical to start off with will help you focus much better on how you're going to achieve that with your students. Andy asks, from a physics teacher's point of view, how can we support students with word equations? And at what point should we introduce symbol equations to students? To help with word equations, it's useful starting to think about some of the suffixes and prefixes we use, such as carbonate, sulfate, sulfide, and how the metal tends to come before the nonmetal in compounds.

Skip to 6 minutes and 22 secondsWe can start introducing those ideas of rules by some of the compounds they know already, like carbon dioxide, iron oxide if they've come across rust, and various other things that are more everyday context for them. We should also really be introducing symbol equations as soon as we can, because that gets students used to the idea of things happening at the atomic level and the idea of bonds being broken and bonds being made when compounds react. Which we need to use as a form of our basis when we look at enthalpy changes later on.

Skip to 6 minutes and 50 secondsAnd also, to a degree, about entropy as well with the number of particles and the order they're in as well, which forms the basis for other things we go into later on. Karen asked a question about teaching equilibrium. And equilibrium is quite a challenging concept for students, particularly as we often link it to rates and we mentioned that earlier on in the course. There are a couple of practicals you can do for looking at the positions of equilibrium. And they can be both found on our website,, under the resources tab. One of these is the cobalt chloride equilibrium. Cobalt chloride is a toxic substance, but it can be made up by teachers or technicians.

Skip to 7 minutes and 29 secondsAnd it can be used in stoppered containers, such as small glass ignition tubes or small test tubes, for students to handle. The cobalt chloride is made up in a mixture of concentrated hydrochloric acid and water. And depending on the concentration of the acid or the concentration of the water, the colour changes from a pink to blue. And it's possible to obtain an intermediate colour where just one drop of hydrochloric acid will send it in one direction, one drop of water will send it in the other colour direction. It's also sensitive to temperature as well.

Skip to 8 minutes and 0 secondsSo standing it in ice cold water and standing it in water that's been boiled from a kettle will give you a colour change that you can see quite clearly. And we can, even without doing the chemistry, talk about the colour changes, whether something's endothermic or exothermic. There is another very good practical which looks at the Chatelier's principle in the gas phase. Where here, you're using carbon dioxide that's dissolved in soda water with an indicator, methyl red. Which when you put it into a syringe, you can reduce the pressure and remove carbon dioxide from the solution, which changes the pH of the solution, and the indicator changes colour.

Skip to 8 minutes and 34 secondsWe can then squeeze that syringe and the carbon dioxide is formed back into the solution where we're then changing the colour by lowering the pH. And we can show that's a reverse of an equilibria in the gas phase which is otherwise quite a challenge for our students to understand. Rose is asking a question about the differences between the equipment setups we use in labs and everyday life, and how they link to everyday activities. And actually, maybe we do need to have a little bit of a difference between those. Because although we do some things that are similar in the home and everyday environments, such as maybe filtering coffee grounds out using filters.

Skip to 9 minutes and 9 secondsWe might talk about we can boil solutions up in the lab on a beaker, but we might use a kettle or a saucepan at home. We need to make those links, actually we're doing the same things. But the reason we're using this equipment is maybe it may be more precise, it may be it's more controlled, we can measure the volumes easy. Not many saucepans have markings for the volume of water inside them, but our beakers do, so therefore we can use them. We can see into our glass beakers and see what's happening, harder to do that with a saucepan.

Skip to 9 minutes and 36 secondsSo we might be sometimes doing similar activities, but the reason we use this setup is for a specific purpose in chemistry. Mark's asked a question about, a suggestion about having a sign on the wall that maybe says, five days without breakage in the lab. And, to be honest, in most of my teaching labs, that would have probably only stuck at one day. And we really shouldn't be trying to scare students off from breaking stuff, breakages do happen. And I think we need to train our students to deal with those breakages, whilst on the other hand also encouraging them to treat equipment fairly and carefully.

Skip to 10 minutes and 10 secondsWe don't want to scare our students and try and make them wrapped up in cotton wool so that they don't actually experience some form of risk. But we also do need to try and train our students that actually, when things do go wrong, they know how to deal with them.

Q&A with Mark

After the supported period for this course, Mark Langley answered a selection of your questions as part of a Q&A session. The Q&A sessions on our courses are your opportunities to post any outstanding questions from your reflection grid, pick up any points from the course in more detail or discuss your teaching context.

Mark’s responses were recorded on 15 March and uploaded on 22 March.


0.10 - Motivating students to learn theory and practical work - Andrew

1.15 - Level of guidance to give students - Christine

2.10 - Learning outcomes focusing on data - Steven

2.47 - What to do when practicals go wrong - Thomas

4.14 - Safe practicals for difficult classes - Thomas

5.12 - Success criteria and learning intentions - Anthea

5.58 - When to move from word equations to chemical formulae - Andy

7.01 - Practicals for equilibrium - Kevin

8.49 - Connecting laboratory equipment with everyday life - Rosa

9.44 - Reducing breakages and lab safety - Mark

Further opportunities

The next run of Teaching practical science: chemistry will be in June. You can participate again then.

Alternatively, you are very welcome to join us on the STEM Group for secondary science teachers where you can network with a community of other teachers and our professional development leaders.

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This video is from the free online course:

Teaching Practical Science: Chemistry

National STEM Learning Centre